Manufacture of articles molded from cellulosic fibrous pulp



Patented June 6, 1939 PATENT OFFICE MANUFACTURE OF ARTICLES MOLDED FROMCELLULOSIC FIBROUS PULP Ivar Bjarne Berghoff, Stockholm, Sweden NoDrawing.

Application February 15, 1937,

Jfierial No. 125,928. In Sweden February 18,

5 Claims.

My present invention relates to a process for the manufacture of moldedarticles, particularly plates or boards for building, furnishing and/orinsulating purposes, and especially of molded 5 articles which havegreat porosity and small specific weight. The plates-have good heat andsound insulating properties but in spite of their great porosity theyshow little or no absorption or adsorption of liquid, when immersed intofor instance water. The invention also includes articles manufacturedaccording to my new process. iAccording to myinvention the articles aremanufactured by forming and drying to sheets or webs of finely dividedmixture of a cellulosic fibrous material and a binding agent, subjectingsaid sheets or webs to such a mechanical treatment as to cause thefibres to be re-loosened from each other, wholly or in part, whileforming a wool-like product, mixing said product with a binding agent ora'mass containing such an agent, for instance original un-dried mixture,and forming the mass'thu's obtained into desired shape, preferably undersupply of heat and ap- 5 -plication of small pressure.

. 'As basic material I may use any suitable cellulosic fibrous material,e. g., grass, straw, esparto, reed, bark, cork and the like, which hasbeen subjected to a defibrating operation before said treatment, orwhich is defibrated during same. In order to obtain a porous product Iprefenhowever, to use pulp obtained by chemical or mechanical treatmentof wood, as for instance mechanical wood pulp in the form of second-ratewood pulp, such as brown wood pulp. As binding agent I may use anysuitable substance having binding properties, but as in most cases thechoice of said agent is dependent of the price obtainable for theproduct produced, I prefer to use as binding agent lime, preferably inthe form of-lime milk, alum and/or resin, either each per se or two ormore thereof admixed with each other. In the manufacture of highlyporous plates having small specific weight the lime may be dispensedwith and only alum and/or resin be used, the latter substance having inaddition to its binding properties also hydrophobe character which is ofadvantage 'for obtaining a product having water repelling character.

My invention will be described in the following as applied to themanufacture of highly porous plates from brown wood pulp .or othersecond-rate wood pulp as basic material, it being observed, however,that my invention may also be applied to the manufacture of plates orboards of harder nature from the same or other basic material.

In a mixing apparatus, which preferably consists of an edge-mill butalso may be a grinding machine, defibrator or similar apparatus, I mixbrown or other second-rate wood pulp with alum (for instance potassiumaluminium sulphate) in a quantity amounting for instanceto 5 to 10% ofthe dry weight of the basic material. Before being mixed with the alumthe basic material may have been subjected 'to a preliminary defibrationin an edge-mill or similar apparatus. The alum may be added in solidstate or in the form of a water solution. In the same edge-mill butpreferably after the addition of the alum, or more preferably in afollowing edge-mill, when using a number of such apparatuses, resin isincorporated into the mixture in a quantity varying with the content ofthe basic material of resins and/or lignines and amounting for instanceto 5% of the'dry weight of the material. In addition to any water addedtogether with the alum I may add during the mixing operation additionalwater into one or more of the edge-mills dependent of the water contentof the basic material. The water content should be kept at a value so asto prevent the rollers of the edgemill from cutting through the materialwhile simultaneously ensuring an effective grinding action. When usingsecond-rate or brown wood pulp in the form in which said pulp leaves thedrainage-drums the water content may be 90% but for the purpose of myinvention it should preferably be at most 80% or still lower, forinstance to 50%. ing the mixing operation should be so adapted as toobtain a final mixture of a water content of at most preferably stilllower, e. g., between 70 and 50%.

When the ingredients are thoroughly mixed the mixture is formed anddried to sheets or webs in any known manner. The drying may be carriedout in an ordinary drying press.

According to the invention I subject the dried product thus obtained tosuch a mechanical treatment as to cause the product to be defibrated,that is the fibres thereof to be reloosened from each other, wholly orin part. This treatment may be carried out in any suitable manner asforinstance by subjecting the sheets or webs to the action of brushes orother grinding members. By this mechanical treatment a woollike productis obtained in which all of the fibres are impregnated by the bindingagent or agents added during the preceding mixing operation.

The addition of Water durdried mixture of the basic material and bindinagent of a suitable water content or together with water, which mixturemay be added' by being sprayed onto the dried product or in any othersuitable manner. The mass thus obtained is then ready for molding whichmay be efiected in a mold or on a plane sieve. i

According to another embodiment of my in-' vention the wool-like productis mixed with undried mixture in a stirring vat or similar apparatus,water being added in such a quantity as to obtain a mixture of aconsistency of about 1 to 5, preferably about 2% by weight of drysubstance. Then the molding operation is carried out in molds or on aplane sieve while removing the water as completely as possible. 1

The addition of the un-dried mixture to the wool-like product may alsotake place in any suitable mixing apparatus while keeping the additionof water as low as possible soas to obtain a mass of a dough-likeconsistency, 'Then the mass is molded by being pressed out-through anozzle.

The proportion between the dried re-defibrated wool-like product and theun-dried product may be to parts by weight of the former to 20 to 10parts by weight of the latter.

The plates or boards obtained by'the molding operation are then dried.This may be carried out in such manner that every separate board isintroduced between two hollow pressing plates of metal such as aluminiumor steel which are heated in any suitable manner, e. g., by means ofsteam. The pressure required may be executed by the own weight of theover-lying pressing plate, or by additional pressure applied in suitablemanner to one or both of the pressing plates. Preferably, several pairsof such pressing plates are provided one above the other so as to forminterspaces between them, into which the fibre boards are introduced. Byproviding stopping studs between the pressing plates all of the fibreboards may be pressed to one and the same desired thickness.

In the embodiment described the magnitude of the pressure should berelatively low, and I also prefer to applyzthe pressure gradually, forinstance by providing springs around the stopping studs. The pressure ofthe steam may originally amount to about 6 kgs. per sq, cm., but whenthe desired thickness of the boards is attained, I may gradually reducethe pressure to about 2 kgs. per sq. cm. thereby preventing the boardsfrom being burnt.

After the boards have been sufficiently dried under supply of heat andapplication of suitable pressure, they are removed from the press andare then ready for use.

Boards manufactured according to my invention have a very low specificweight of .12 to .10 and still lower, for instance .085 as well as goodheat and sound insulating properties.

articles, which comprises mixing a cellulosic fibrous material with alumand a binding substance having hydrophobe character so as to form afinely divided mixture, forming sheets of'said mixture and drying saidsheets, subject- 7 ing said dried sheets to such a mechanical treatmentas to cause the fibres to be re-loosened, at least in part, whileforming a wool-like product, mixing a quantity of said product with aquantity of a binding agent, and forming the mass thus obtained intodesired shape under heat.

2. A process for the manufacture of molded articles, which comprisesmixing a cellulosic fibrous material first with alum and then with resinso as to form a finely divided mixture, forming sheets of said mixtureand drying said sheets, subjecting said dried sheets to such amechanical treatment as to-cause the fibres to be-re-loosened, at leastin part, while forming a wool-like product, mixing a quantity of saidproduct with a quantity-of a binding agent, and forming the mass thusobtained into desired shape under heat.

3. A process for the manufacture of molded articles, which comprisesmixing a cellulosic fibrous material with alum and resin so as to form afinely divided mixture, forming sheets of said mixture and dryingsaidsheets, subjecting said.

articles, which comprises mixing a cellulosic fibrous material withlime, alum and resin so as to form a finely divided mixture, formingsheets from said mixture and drying said sheets, subjecting said driedsheets to such a mechanical treatment as to cause the fibres to bere-loosened from each other, at least in part, while forming a wool-likeproduct,.mixing a quantity of'said product with a quantity of a bindingagent, and forming the mass thus obtained into desired shape under heat.

5. A process for the manufacture of molded articles, which comprisesmixing a oellulosic fibrous material with lime, alum and resin so as toform a finely divided mixture, forming sheets from said mixture anddrying said sheets, subjecting said dried sheets to such a mechanicaltreatment as to cause the fibres to be re-loosened from each-other, atleast in part, while forming a wool-like product, mixing a quantity ofsaid product with a quantity of the original un-dried mixture, andforming the mass thus obtained into desired shape under heat.

IVAR BJARNE BERGHOFF.

